Pilotless, unplugged combustion control system

ABSTRACT

A self-powered combustion control system having a burner and a fuel supply control valve connected with the burner. The fuel supply control valve includes ignition and hold solenoids arranged whereby energizing the ignition solenoid causes the hold solenoid to transform from a closed disposition in which no fuel passes to the burner to an open disposition in which fuel flow to the burner is initiated for igniting the burner and subsequently maintained during heating of the material to be heated. An electronic system controller is provided for controlling the ignition solenoid and an unpowered rechargeable energy storage device is provided for all of the power required to operate the combustion control system.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an automatic, self-sufficient combustioncontrol method and system. In one aspect, this invention relates tofuel-fired heating equipment and appliances. In one aspect, thisinvention relates to electric-powered flow control valves. In yetanother aspect, this invention relates to automatically controlled,unplugged water heaters.

2. Brief Description of Related Art

Approximately 56 million households in the United States and Canada usea non-powered atmospheric gas fired water heater to meet their domestichot water needs. Each water heater consumes on average about 200 thermsannually. One therm is equal to 100,000 Btu (British thermal units). At450 Btu/hr, the water heater pilot light represents 20 percent of thegas use, or about 39 therms. If it is assumed that one-third, about 6.5therms, is unused energy, the annual total waste energy from these pilotlights is 3.6 billion cubic feet of natural gas.

The current mechanism for eliminating the pilot light requires a powered(plugged) connection. However, a powered connection adds about $100 tothe cost of the water heater and the cost of initially bringing power tothe water is approximately $150. Thus, it is apparent that a transitionfrom pilot-based water heaters to pilotless water heaters will saveenergy, save installation and retrofit costs, and reduce combustionemissions.

U.S. Pat. No. 6,561,138 teaches a conventional water heater comprising ahot water storage chamber in the top portion of a tank and a combustionchamber in the bottom portion of the tank. A fuel flow controller, whichcontrols fuel flow to the main water heater burner and a pilot flame, isconnected to a fuel supply line. A water heater thermocouple and a pilotflame thermocouple constitute the input sensing elements for thecontroller. The fuel control valve comprises inlet and outlet flowpassages connected by a valve seat orifice. An opening and closing valveplunger is pressed on the valve seat by a coil spring. Additionally, arod on which the valve is mounted is attached to a metal platepositioned proximate a fixed electromagnet which is connected to thethermocouple used for monitoring the burner. The magnet generates apredetermined magnetic force when normal ignition of the burner isdetected. An ignition button is manually pressed at the time of thewater heater startup to provide fuel flow through the valve. Once aflame is sensed and a current established, the fixed electromagnet isenergized, thereby holding the valve plunger in an open position. If,for some reason, the flame goes out, the fixed electromagnet isde-energized, causing the valve plunger to move to a closed position,thereby shutting off fuel flow to the burner.

U.S. Patent Application Publication No. US 2003/0177818 teaches a waterheater having a float activated electrical switch positioned in a watercollection pan to automatically shut off both an electrically activatedwater supply valve and a gas shutoff valve in the event of a water leak.The water heater further comprises an adaptive connector for providingelectrical connection between the gas control valve and a flamethermocouple and a normally closed relay for interrupting a thermocouplevoltage supplied to the gas control valve.

U.S. Pat. No. 6,684,821 teaches a water heater having a pilot burner andtwo thermo-voltaic devices proximate the pilot burner electricallyconnected with a pilot gas valve through which fuel is provided to thepilot burner, wherein the pilot flame from the pilot burner providesheat energy to the thermo-voltaic devices which, in turn, createelectrical energy to hold open a pilot valve located in the pilot gasvalve. The pilot flame remains lit the entire time that the water heateris in operation.

U.S. Pat. No. 6,261,087 teaches a burner system for use in applicationssuch as a gas fireplace insert having a main burner, a standing pilotburner, a burner control unit, and a fuel valve in which the fuel valveand burner control unit receive power from a power source such as athermopile mounted to receive energy from the pilot burner. The burnercontrol unit includes a switch for controlling power to the fuel valveand an RF receiver, thereby enabling operation of the system remotelyusing an RF transmitter.

U.S. Pat. No. 6,257,871 teaches a device for controlling a gas-firedappliance having a thermoelectric device such as a thermopile forcontrolling a millivolt vent damper and a main burner within thegas-fired appliance. The device includes a control circuit thatselectively transmits current from the thermoelectric device to the mainburner valve of the appliance and a damper motor. The control circuitalso includes a temperature sensor and a plurality of single pole doublethrow switches. When the temperature sensor determines that thetemperature of the medium to be heated is below a predeterminedtemperature, current is directed through the switches to the motor toopen the damper, following which current is redirected through theswitches to the valve to open the valve. When the predeterminedtemperature has been reached, current is again directed to the motor toclose the damper and trap residual heat within the appliance.

SUMMARY OF THE INVENTION

It is one object of this invention to provide a combustion controlsystem for material or medium heating appliances which isself-sufficient, requiring no external energy input.

It is one object of this invention to provide a combustion controlsystem for material or medium heating appliances which includes energystorage capabilities.

It is yet another object of this invention to provide a combustioncontrol system for material or medium heating appliances which is ableto operate on less than 3 watts of energy.

These and other objects of this invention are addressed by aself-powered combustion control system comprising a burner and a fuelsupply control valve having a fuel outlet in fluid communication withthe burner. The fuel supply control valve comprises an ignition solenoidand a hold solenoid. The ignition solenoid is operationally linked withthe hold solenoid such that energizing the ignition solenoid causes thehold solenoid to transform from a closed disposition, i.e. anon-energized condition, in which no fuel passes to the burner to anopen disposition in which fuel flow to the burner is initiated forigniting the burner and subsequently maintained during heating of thematerial to be heated. The system further comprises an electronic systemcontroller for controlling the ignition solenoid operationally connectedwith the ignition solenoid and an unpowered energy storage deviceproviding all of the power required to operate the combustion controlsystem. In accordance with one embodiment, the system comprises meansfor recharging the low power energy storage device.

The primary benefits of this invention include higher system efficiencyand lower energy consumption due to the elimination of the pilot burnerused with conventional systems, reduced standby power consumption,reduced emissions, avoidance of electric line power use, and stable andsafe operation during power outages. Whereas conventionalself-generating technologies rely on pilot burners as a primary sourcefor thermoelectric generation, the system of this invention employs aburner for this purpose that is constantly on during heating of thematerial to be heated. In addition, whereas conventional self-generatingtechnologies may rely on other power sources or battery change outduring the life of the appliance, the system of this invention requiresno external energy sources and no battery change out.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of this invention will be betterunderstood from the following detailed description taken in conjunctionwith the drawings, wherein:

FIG. 1 is a schematic diagram of a self-powered combustion controlsystem in accordance with one embodiment of this invention;

FIG. 2 is a diagrammatic representation of a low power valve operatingsequence employed in the self-powered combustion control system inaccordance with one embodiment of this invention;

FIG. 3 is a schematic diagram of a circuit for ignition of the burner ofa water heater in accordance with one embodiment of this invention;

FIG. 4 is a schematic diagram of a circuit for controlling the fuelsupply control valve in accordance with one embodiment of thisinvention; and

FIG. 5 is a flow diagram for a program integral with the electronicsystem controller for controlling the combustion control system inaccordance with one embodiment of this invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

The invention disclosed herein is a combustion control system forfuel-fired heating equipment and appliances which conventionally employa pilot burner and pilot flame for ignition of the main burner employedtherein, including gaseous fuel-fired residential and commercial waterheaters and gas-fueled fireplaces, which eliminates the need for a pilotburner and pilot flame. Although the system generally is describedherein for use with a water heater, it will be appreciated that thesystem as described may be employed in any heating apparatus orappliance which conventionally uses a pilot flame and burner for mainburner ignition, and such applications are to be understood to be withinthe scope of this invention. Included within the range of applicationsto which this invention may be applied are residential, commercial, andindustrial water heaters, residential and commercial space heaters andwall furnaces, residential and commercial stoves and ovens, gas-firedfireplaces with thermostatic or on/off remote control, outdoor livingappliances including gas lighting, grills, patio heaters, and fire pits,and agricultural applications such as orchard heaters.

Accordingly, the combustion control system in accordance with oneembodiment of this invention used in a water heater comprises a lowpower consumption fuel supply control valve and control/ignitionmanagement hardware as well as conventional elements widely availableand used in tank-type water heaters, such as a spark igniter,thermocouple or thermopile, water temperature sensor, and the like. Bylow power consumption, we mean less than or equal to about 10 J ofenergy for each ignition cycle. The fuel supply control valve of thisinvention incorporates housing, plunger, and control elements similar toconventional water heater fuel supply control valves, thereby ensuringlow cost and high safety of the disclosed system. In contrast toconventional systems which typically require human intervention toignite the pilot flame, the additional control elements of thecombustion control system of this invention provide on-demand ignition,shutdown, and automatic shutdown in the event of flame loss or powerloss without human intervention.

The combustion control system in accordance with one embodiment of thisinvention as shown in FIG. 1 comprises a fuel valve 10 having a holdsolenoid 11 having an open, energized disposition and a non-energizeddisposition and an ignition (startup) solenoid 12 having an energizedigniting mode and a non-igniting mode, a burner 13, an electronic systemcontroller 14 operationally connected with the ignition solenoid 12, andan unpowered rechargeable low power energy storage device 15 connectedwith electronic system controller 14 and providing all of the powerrequired to operate the combustion control system. As used herein, theterm “unpowered” refers to a condition in which no power is provided tothe system by an external power source, such as an electrical line.Thermocouple 16 is provided for detecting the presence of a flameproduced by burner 13 and is operationally connected with hold solenoid11. Flame sensing spark igniter 17 connected with electronic systemcontroller 14 provides a spark for ignition of the fuel provided toburner 13. As shown in the exemplary embodiment of FIG. 1, the system isused to provide heat to water tank 18 having water temperature sensor 19operably connected with electronic system controller 14. In accordancewith one embodiment, a thermoelectric system operationally connectedwith low power energy storage device 15 is provided for recharging thelow power energy storage device. Suitable recharging systems includethermopiles and integral hydro-generators. In accordance with oneembodiment of this invention, the low power energy storage device is abattery. In accordance with another embodiment of this invention, thelow power energy storage device is a supercapacitor or capacitor.

Hold solenoid 11 is operationally linked in accordance with oneembodiment of this invention by a shaft or rod 23 with ignition solenoid12 such that when the ignition solenoid is in the energized ignitingmode, the hold solenoid is in an open disposition. The open dispositionof the hold solenoid corresponds to a position, shown in FIG. 1, inwhich the fuel supply control valve is open, enabling fuel to flow tothe burner. Energizing of the hold solenoid is maintained by a signalgenerated by thermocouple 16 when a flame from the burner is present.Hold solenoid 11 includes a spring 21 and plate 22. In the event thatthe flame should be extinguished, the spring acts to push the platetoward the valve opening, thereby shutting off fuel flow. Duringignition of the burner, the ignition solenoid, by way of shaft or rod23, pushes against plate 22 of the hold solenoid, contracting the springand causing the hold solenoid to assume an open disposition, therebyallowing fuel to flow to the burner for ignition by flame sensing sparkigniter 17. Once the burner is lit, the ignition solenoid isde-energized and the hold solenoid is energized, enabling the continuousflow of fuel to the burner. In accordance with another embodiment ofthis invention, the ignition solenoid and hold solenoid may be in thesame windings such that energizing the ignition solenoid results in apulling of the plate 22 against the force of the spring to open the fuelsupply control valve and de-energizing of the hold solenoid results inpushing of the plate by the spring to close the fuel supply controlvalve.

The spark ignition sequence is synchronized by the electronic systemcontroller 14 with the energizing of the ignition solenoid. Duringignition, the flame is monitored by measuring interelectrodeconductivity of the electrodes of the flame sensing spark igniter 17.The flame ignition and stabilization results in heating of thethermopile source, e.g. thermocouple 16, that provides power to the holdsolenoid similar to the design implemented in conventional water heatersystems. The fuel supply can be interrupted by the electronic systemcontroller by interruption of the hold solenoid circuit, which resultsin closing of the fuel valve. The electronic system controller initiatesignition and extinguishes the flame to maintain a desired water tanktemperature that can be time-programmed to minimize energy consumption.

Operating sequence of the low power fuel valve of this invention isshown in FIG. 2. The sequence is initiated by an ignition request fromthe electronic system controller which starts a series of ignitiontrials, each of which trials involves light up of the flame sensingspark igniter for a predetermined time interval. The ignition solenoidis in an energized igniting mode and the hold solenoid is in anon-energized open disposition, being acted upon by rod 23, during thespark operation to allow the supply of fuel to the burner. The ignitiontrials are repeated several times until successful ignition is achievedor until a predetermined maximum number of ignition trials has beenreached. Flame ignition is monitored by an ion conductivity sensor whichmeasures the resistance across the spark gap. A drop in the resistancecorresponds to flame ignition. The positive signal of the flame monitorcauses a delay in the ignition solenoid shutoff, i.e., return to anon-igniting mode, which delay is sufficient for providing flamestabilization and for preheating of the thermocouple sensor. In turn,the hot thermocouple sensor provides enough electrical power to maintainthe hold solenoid in the open disposition. At this point, the ignitionsolenoid is deactivated (de-energized) and the fuel supply control valveis held open by the signal from the thermocouple sensor, whichessentially reduces the power drawn from the power source. Thethermocouple sensor constantly monitors flame operation, and if theflame is extinguished, the thermocouple sensor, no longer sensing thepresence of the flame, deactivates the hold solenoid, shutting off thefuel supply line. This operating sequence may be repeated by theelectronic system controller monitoring the water temperature, waterlevel, and other external factors. It will be appreciated that power isconsumed by the system only during ignition of the flame. During theremaining portion of the cycle, power to the hold solenoid, and, thus,the fuel supply control valve, is supplied by the thermocouple sensor.In accordance with one embodiment of this invention, a portion of theelectrical power produced by the hot thermocouple sensor also may beused to recharge the energy storage device.

The fuel supply control valve of this invention requires about 10 J ofenergy per activation of the ignition solenoid and, as previouslyindicated, the energy for holding the hold solenoid is provided by aconventional thermocouple source. Thus, an energy storage device with acapacity of about 1000 kJ will permit more than 100,000 ignition cycles.Also, as previously indicated, the energy storage device is preferablyrechargeable. However, batteries employed as storage devices inaccordance with one embodiment of this invention may merely be swappedout for a new battery rather than recharged, if desired.

FIG. 3 shows an exemplary circuit for controlling the power and holdingtime intervals of the ignition solenoid and hold solenoid in accordancewith one embodiment of this invention. Other circuits may be suitablefor this purpose as well. The circuit comprises a time relay K1 (ModelH3CA, Omron, Inc.) operating as an “interval on relay” (Mode C). The ONstate of the relay is activated by application of power and may be setfrom 0.1 seconds to a few hours. At the end of the ON state, the relayis switched off and the power to the ignition solenoid is supplied via abypass resistor. The value of the resistor is preferably selected toprovide the minimum voltage required for holding the solenoid. A bypassresistor with a value of 72 ohms is shown in FIG. 3. Using this circuit,a time interval of only 0.1 seconds is sufficient to complete the powerstroke of the solenoid. After that, the control voltage may be reducedto as low as 2 VDC, allowing for significant power saving during anignition cycle. The power and energy requirements for a single ignitioncycle of the lower power valve are shown in Table 1.

TABLE 1 Power and energy requirements for a single flame ignition cycleRegime Duration, s Voltage, VDC Power, W Energy, J Power stroke 0.1 2438 3.8 Hold 20 2 0.25 5

As shown therein, the power dissipated during the power stroke, i.e.fuel valve activation, is equal to about 38 W. However, the power strokeduration is only 0.1 seconds, resulting in a total energy input of about3.8 J. A holding time is defined by a characteristic thermal constant ofa thermopile sensor used in the control circuit. This time is typicallyclose to 20 seconds. However, the power required for holding thesolenoid is only 0.25 W; so, the energy input during the holdinginterval may be evaluated as about 5 J. As a result, the overall energyinput from a battery source would be below about 10 J.

FIG. 4 shows a valve control circuit suitable for controlling the fuelvalve using battery power. This microprocessor controlled circuit isdesigned for direct burner supervision and provides ignition sequence,flame monitoring, and safety shutdown for intermittent water heaters andother heating appliances. To satisfy the battery powered operationrequirement, a DC/AC converter and a low power 120/240VAC transformerare included in the circuit. The circuit includes a commercial ignitionmodule (Model 23114, Capable Controls, Inc.). The control module has a“Pilot Valve” output signal which is activated at the beginning of anignition cycle and a “Main Valve” output signal which is activated aftera successful ignition event is detected by the flame sensing circuit.The circuit includes two time relays K3 and K4 to control the durationsof the power stroke and the initial solenoid holding time. These relaysare “interval on relays” that are activated by application of power tothe relay inputs. By way of example, relay K3 may be set for a timeinterval of 0.1 seconds and relay K4 may be programmed for a holdingtime interval in the range of about 5 to 60 seconds.

Flame ignition and sustainment tests using this circuit have beenperformed using a “pancake-type” burner commonly used in conventionalresidential gas-fired water heaters. The burner was connected with acompressed methane supply and a pressure regulator was used to drop thepressure of methane to about 4″ of water column. The ignition sequencewas initiated by a control circuit that activated the ignition solenoid,thereby initiating a spark discharge. A soft start of the system wasprovided by ignition of a pilot flame which was supported for the periodof time required to preheat the thermopile. The main flame was ignitedat the end of the ignition cycle, at which time power to the ignitionsolenoid was terminated, allowing gas flow to the main burner. The fuelsupply control valve was maintained open by the thermopile sensor. Aflame interruption resulted in fast thermopile cool down and closure ofthe fuel supply control valve.

While in the foregoing specification this invention has been describedin relation to certain preferred embodiments thereof, and many detailshave been set forth for purpose of illustration, it will be apparent tothose skilled in the art that the invention is susceptible to additionalembodiments and that certain of the details described herein can bevaried considerably without departing from the basic principles of theinvention.

We claim:
 1. A self-powered combustion control system comprising: aburner; a fuel supply control valve having a fuel outlet in fluidcommunication with said burner and having an ignition solenoid and ahold solenoid, said ignition solenoid and said hold solenoid operablylinked, whereby energizing said ignition solenoid causes said holdsolenoid to transform from a closed disposition to an open disposition;an electronic system controller for controlling said ignition solenoidoperably connected with said ignition solenoid; and an unpowered energystorage device providing all power required to operate said combustioncontrol system.
 2. The system of claim 1, wherein said unpowered energystorage device is rechargeable.
 3. The system of claim 2, wherein saidunpowered energy storage device is a supercapacitor.
 4. The system ofclaim 2, wherein said unpowered energy storage device is a battery. 5.The system of claim 1 further comprising an igniter for igniting saidburner operably connected with said electronic system controller.
 6. Thesystem of claim 1 further comprising a flame presence sensor proximatesaid burner operably connected with said hold solenoid, whereby heatingof said flame presence sensor maintains said hold solenoid in said opendisposition.
 7. The system of claim 1 further comprising a heatingvessel for holding contents to be heated.
 8. The system of claim 7,wherein said heating vessel is a water tank.
 9. The system of claim 7further comprising a temperature sensor suitable for measuring atemperature of said contents operably connected with said electronicsystem controller.
 10. The system of claim 1 further comprising athermoelectric system operably connected with said unpowered energystorage device for recharging said energy storage device.
 11. The systemof claim 10, wherein said thermoelectric system comprises a thermopileor thermocouple.
 12. The system of claim 11, wherein said thermopile orthermocouple is operably connected with said hold solenoid formaintaining said hold solenoid in said open disposition.